Liaodong Bay Research Articles

The compositions of biomarkers and macerals in the first member of the Shahejie Formation in the Liaodong Bay subbasin, Bohai Bay Basin: Implications for biological sources and seawater incursions

Seven mudstone/shale core samples were collected from the first member of the Shahejie Formation (E2s1) in this study, which is considered as a potential source rock in the Liaodong Bay subbasin. The biological sources and sedimentary environments of the E2s1 source rocks were studied based on the analyses of organic geochemistry and organic petrology. The results indicate that E2s1 source rocks were deposited in a lacustrine environment with relatively high salinity, which caused the stratification of water body and anoxic bottom conditions. The abundant and stable presence of regular steranes, dinosteranes, 4α-methyl-24-ethylcholestanes, 24-norcholestanes, 24-n-propylcholestanes, hopanes, 2α-methylhopanes, and 3β-methylhopanes in the studied samples indicate that dinoflagellates, diatoms, pelagophyceae, cyanobacteria, rhizobiales and aerobic methanotrophs were the main biological sources of the E2s1. Among them, dinoflagellates are closely related to the formation of organic-rich E2s1 source rocks, which is supported by the positive correlation between TOC or HIvalues and 4α-methyl-24-ethylcholestane (biomarker of dinoflagellates) contents. Trace amounts of terrestrial higher plant biomarkers in the studied samples indicated that their contributions to organic matter were limited. This is consistent with the abundance of lamalginite and mineral-bituminous groundmasses observed in the E2s1 samples under optical micrographs. Widely occurring marine incursion events in the Eocene in the Bohai Bay Basin may have also occurred during the deposition of the E2s1 in the Liaodong Bay subbasin, supported by the presence of a typical marine pelagophyceae biomarker (24-n-propylcholestane).

Radium isotope assessment of submarine groundwater discharge and associated nutrient inputs in Eastern Liaodong Bay, China

The accurate assessment of submarine groundwater discharge (SGD) and associated nutrient fluxes plays a significant role in water resources management and ecological environment protection in the coastal area. Currently, Liaodong Bay has become one of the most polluted marine areas in China. However, the nutrient fluxes carried by the SGD and its environmental effects have not yet been thoroughly reported in eastern Liaodong Bay, China. In this study, the distribution of 224Ra/223Ra activity ratio and its influencing factors under the geochemical conditions were explored. The activity of radium was affected by the water type and the geochemical factors. The radium isotopes in seawater were positively correlated with the ratios of Mg2+/Na+ and Ca2+/Na+ but negatively correlated with salinity and SO42−. The average apparent water age was evaluated to be 13.0 days. Furthermore, based on the radium mass balance model, the total average SGD flux was calculated to be 1.31 × 108 m3 day–1. The nutrient fluxes carried by the SGD were 7.16 × 107, 1.01 × 106, 1.61 × 107, 0.92 × 106, and 5.41 × 107 mol day−1 for DIN, DIP, NH4+, NO2−, and NO3−, respectively. The nutrient inputs through the SGD have an average DIN : DIP ratio of 70, which was able to seriously affect the ecological environment. The SGD-derived nutrient fluxes were higher than the local river input, which demonstrated that the SGD was a major source of nutrients affecting regional marine ecosystems.

Late Quaternary sedimentation and neotectonics in Liaodong Bay, northern Bohai Sea

The Bohai Sea is a typical shelf sea, with obvious sediment differences in different regions. Although Liaodong Bay is the largest bay in the Bohai Sea, there lacks boreholes with precise dating. In this paper, the core sediments taken from YKC-2 borehole in the northeastern of Liaodong Bay are dated with AMS14C and OSL, in addition to grain size analysis, foraminifera and pollen identification, lithological characteristics and other testing results. Correlation is made with the global sea level change curve, and upon the basis the evolution of paleoenvironment in the northeast of Liaodong Bay is reconstructed. It is speculated that the age of the bottom of borehole YKC-2 is 150 kyr B.P., and two transgressions have been recorded, similar to the situation in JXC-1, a borehole 46.7 km to the west. It can be found that the sedimentation rate of YKC-2 borehole is obviously higher than that of JXC-1. The authors’ research found that it is mainly controlled by two factors: the provenance difference and the differential movement of basin controlling faults. In the west, sediments are mainly transported by the Bohai Sea current, with insufficient sediment supply, and the basin-controlling faults are rather stable and very weak in activity. In the east, sediments are transported mainly by the surrounding rivers with sufficient sediment supply; and the changes in accommodation space are under the control of the Tan-Lu fault zone. Affected by the strong extensional dynamic environment of the Bohai Bay Basin, the accommodation space, where the borehole YKC-2 is located, continuously increased for deposition of near-source river sediments. This article is an endeavor to study the evolution of the Late Quaternary sedimentary environment and the influence of tectonic activity on Quaternary sedimentation in the Bohai Sea.

On the Method of Design Drift-Ice Concentration and Floe Area for New-Energy Structures in Ice-Infested Nearshore Areas of the Bohai Sea, China

To provide basic drift-ice parameters for new-energy structures in ice-infested nearshore waters, an estimation method of the design drift-ice concentration and floe area was established. A total of 700 satellite images in winters from 2010 to 2021 were used to obtain the drift-ice concentration and floe area from 26 sites in the Bohai Sea. The floe area with 90% cumulative probability was selected as the characteristic floe area in each satellite image. Furthermore, the water temperature threshold ranging from −1.6 °C to −0.5 °C was adopted by considering the drift-ice freezing/melting states because of different salinity values in nearshore waters. The upper limit values of the ice concentration and characteristic floe area at the lowest water temperature of −1.6 °C were finally used as the design drift-ice indexes. The maximum design ice concentrations (floe area) in the Liaodong Bay, Bohai Bay, and Laizhou Bay were 96% (0.43 km2), 91% (0.39 km2), and 87% (0.29 km2), respectively. The design ice concentration at the bay bottom was higher than that near the mouth. The design floe area in the Liaodong Bay and Bohai Bay increased with latitudes, but the trend was opposite in the Laizhou Bay. The method developed in the current study has universal applicability, which can be extended to other ice-cover waters and specific structure designs by adjusting the cumulative probability threshold and the water temperature threshold.

Accurate identification of key VOCs sources contributing to O3 formation along the Liaodong Bay based on emission inventories and ambient observations

In order to achieve the precise control of the volatile organic compounds (VOCs) species with high ozone (O3) formation contribution from key sources in Panjin and Yingkou, two coastal industrial cities with severe O3 pollution along the Liaodong Bay, northeast China, the ambient concentrations of 99 VOCs species were measured online at urban-petrochemical (XLT), suburban-industrial (PP), and rural (XRD) sites in July 2019, contemporary monthly anthropogenic VOCs emission inventories were developed. The source contribution of ambient VOCs resolved by positive matrix factorization (PMF) model was comparable with emission inventories, and the location of VOCs sources were speculated by potential source contribution function (PSCF). 17.5 Gg anthropogenic VOCs was emitted in Panjin and Yingkou in July 2019 with potential to form 54.7 Gg-O3 estimated by emission inventories. The average VOC mixing ratios of 47.1, 26.7, and 16.5 ppbv was observed at XLT, PP, and XRD sites, respectively. Petroleum industry (22 %), organic chemical industry (21 %), and mobile vehicle emission (19 %) were identified to be the main sources contributing to O3 formation at XLT site by PMF, while it is organic chemical industry (33 %) and solvent utilization (28 %) contributed the most at PP site. Taking the subdivided source contributions of emission inventories and source locations speculated by PSCF into full consideration, organic raw chemicals manufacturing, structural steel coating, petroleum refining process, petroleum products storage and transport, off-shore vessels, and passenger cars were identified as the key anthropogenic sources. High O3-formation contribution sources, organic chemical industry and solvent utilization were located in the industrial parks at the junction of the two cities and the southeast of Panjin, and petroleum industry distributed in the whole Panjin and offshore areas. These results identify the key VOCs species and sources and speculate the potential geographical location of sources for precisely controlling ground-level O3 along the Liaodong Bay.

A review of sources, status, and risks of microplastics in the largest semi-enclosed sea of China, the Bohai Sea

The largest semi-enclosed sea of China, the Bohai Sea, serves as an important sink of microplastics (MPs) originated from terrestrial and marine sources. This study summarized potential sources and migration pathways of MPs in the Bohai Sea and reviewed the abundance and characteristics of MPs in water, sediments, and organisms. Coastal anthropogenic activities (i.e., plastic production, agricultural activities, and industrial and domestic sewage discharge) and marine origins (i.e., aquaculture, marine litters, and transportation) might accelerate the MPs enrichment in the Bohai Sea. The abundance of MPs ranged from 0.07 to 5200 items/m3 in the seawater, mainly influenced by the application of different trawl nets/sieves with different sizes (0.005–0.33 mm). Sediments of coastal rivers contained the MPs ranging from 56.7 to 1795 items/kg, significantly higher than that of the Bohai Sea (6.24–461.6 items/kg). Among organisms, the average abundance of MPs was the lowest in zooplanktons (0.03 items/animal), significantly lower than that in invertebrates (1.39 items/animal) and fish (2.12 items/animal), but no biomagnification of MPs was observed. The preliminary risk assessment indicated that seawater in the Liaodong Bay had medium ecological risk of MPs while other bays of the Bohai Sea had minor risks. To make the ecological risk of MPs quantifiable and comparable, future research priorities are recommended to focus on more frequent field surveys, standardization of sampling methods, and establishment of toxicity database of common polymer types of MPs in the Bohai Sea.

Holocene vegetation history and responses to climate and sea-level change in the Liaohe Delta, northeast China

To reconstruct the Holocene vegetation history from Liaohe Delta in northeast (NE) China, a high-resolution palynological study on a well-dated sediment core ZK2 was conducted. The pollen record of ZK2 suggests that during the early Holocene, the regional vegetation in the plain was meadow-dominated by Artemisia. And forest with cool-temperate conifers and temperate broad-leaved trees were present in the nearby hills, which is coincident with the gradual climate warming and delta transgression. From mid-Holocene to early late Holocene, meadow vegetation with Artemisia was relatively stable, while the forest vegetation with broadleaved trees reached the maximum expansion in the nearby hills. The large expansion of broadleaved trees indicates warm and humid regional environmental conditions and this is coincidental with the relatively high regional sea-level stand during this period. Since ca. 1470 cal yr BP, with the continuous delta progradation, a large coastal region was colonized by Suaeda spp., which suggests that the formation of unique red beach wetlands along the coastal region of the Liaohe Delta. By analysis of pollen dispersal and transportation mechanism in surface sediments of Liaodong Bay, it is indicated that the percentage changes of arboreal pollen dominated by Pinus and Quercus and the non-arboreal pollen dominated by Amaranthaceae and Artemisia in core ZK2 may as an index refers to the local sea level oscillation and paleoclimate change. Then by comparison with previous multi-proxy records together with the surface sediment record from Liaodong Bay, it is suggested that the Holocene vegetation changes of the Liaohe Delta are mainly driven by the intensity changes of East Asia monsoon and regional sea-level oscillation.

Source apportionment and specific risk assessment of heavy metals in sediment: Application to the Typical Bay, China

In order to expound the spatial distribution characteristic, sources and potential ecological risk of Heavy Metals in Liaodong Bay, China, the surface sediments were collected to be analyzed from 61 sites. The research results showed that the spatial distribution characteristic of heavy metals concentration in Liaodong Bay was obviously discrepant, where the north was higher than the south, and the west was higher than the East. The ecological risk status of Liaodong Bay sediment was at the level of “Moderate Risk”. Hg and Cd were the main factors of pollution that caused the highest ecological risk. Source apportionment of heavy metal indicated that Hg and Cd in Liaodong Bay sediments might be introduced by petrochemical industry projects and offshore oil and gas development activities. Pb, Zn and Cu mainly came from the use of fossil fuels and chemical production processes, while As mainly came from agriculture.

E&P Notes (June 2022)

E&P Notes (June 2022)

The fault activity, tectonic subsidence history, and geodynamics of syn‐depositional faults during the Palaeogene in Liaodong Bay, Bohai Bay Basin

The fault activity, tectonic subsidence history, and geodynamics are analysed based on borehole information and seismic datasets from Liaodong Bay. The results reveal that the faults are intensely active (resulting in the faults that are characterized by more lengths and more throws) both in the northern and southern portions of the study area, while the faults are not active in the central portion of the study area during Kongdian Formation and Shahejie Formation deposition. However, the faults are generally more active in the northern portion of the study area than that in the southern portion of the study area. In contrast, the faults are intensely active in central and southern portion of the study area during Dongying Formation deposition. The numerous syn‐depositional faults, which are intensely active, result in southward movement of depositional centre. The tectonic subsidence history of wells (including well JZ‐A, well JZ‐B, well JZ‐C, well JZ‐D, well JX‐A, and well SZ‐A) in Liaodong Bay indicates that it shows obvious episodic tectonic evolution during the Palaeogene in Liaodong Bay. The episodic tectonic movement (initial rifting, rifting climax, thermal subsiding, and strike‐slip rifting) corresponds to Kongdian Formation and Shahejie Formation deposition, and Dongying Formation deposition, respectively. The spatio‐temporal variation of tectonic subsidence history is closely related to fault activity. The analysis results of balanced cross‐sections show that faults are intensely active during Dongying Formation deposition. However, a few faults are much active than that during Shahejie Formation deposition. There is a slight decrease in tectonic activity intensity during Kongdian Formation and Shahejie Formation deposition. In contrast, there is a significant decrease in tectonic activity intensity during third‐member to first‐member of Dongying Formation deposition. The tectonic activity intensity tends to cease by the end of Dongying Formation.

Spotted seals (Phoca largha) harbor unique gut microbiota shaped by their host habitat

Assessing the structure and composition of gut microbiota of sentinel species such as spotted seals (Phoca largha) is a potential tool for assessing the health of the marine mammals and their habitats. However, the link between the host microbiome and their habitat is poorly understood. In this study, microbial communities in the habitat (sea ice and water) and marine mammalian host (fecal matter from P. largha) were evaluated in samples obtained from the Liaodong Bay, China during population aggregation period. Results from high-throughput sequencing showed that the bacterial communities in P. largha fecal matter were less rich and diverse compared to those from the water and ice samples. Significant differences in the composition and function of bacterial communities were also found among the water, ice, and fecal samples, in which sample type and sampling site had the greatest impact on composition and function variations, respectively. Several potential pathogenic bacteria and bacteria with functions associated with human disease were significantly enhanced in the communities of P. largha feces compared to those of surrounding environments. The ratios of environmental microorganisms sourced from the P. largha fecal matter were estimated. The results showed that certain bacteria in P. largha-inhabited fecal matter were associated with sea ice and had specific antibiotic resistance and infectious capacity. These findings provide critical data for monitoring the health of marine mammals and their habitats, which is essential for predicting the impact of anthropogenic disturbances on marine ecosystems.

New Insights into the Distribution and Evolution of WNW-Directed Faults in the Liaodong Bay Subbasin of the Bohai Bay Basin, Eastern China

WNW-directed faults are widespread in eastern China, but debates regarding their distributions and evolutionary processes remain unsettled. Based on the latest 3-D seismic data, a series of WNW-directed faults south of the Liaodong Bay subbasin was identified, for which the evolution and formation mechanisms were discussed. The results show that four WNW-directed faults are characterized by poor continuity and nearly parallel orientations. Vertically, they exhibit listric geometries and cut through Paleozoic and Mesozoic formations. Since the late Triassic, these faults began as reverse faults under nearly S-N horizontal compression. In the Jurassic, those faults maintained their reverse-faulting activities with dramatically decreased intensities. In the Early Cretaceous, the WNW-directed faults were changed into normal faults under regional extension and were influenced by the sinistral strike-slip movement along the Tan-Lu fault zone. In the Late Cretaceous, the WNW-directed normal faults probably stopped moving due to a regional compressional event. During the Paleogene, the WNW-directed faults were reactivated with decreased intensities and were cut by NNE-directed faults. Here, we emphasize that the evolution of the WNW-directed faults could shed light on the regional tectonics. The WNW-trending faults that developed in the Liaodong Bay subbasin are closely related to the faults in the Yanshan orogenic belt. Therefore, investigating the characteristics and origin of WNW-induced faults will provide evidence for the tectonic evolution of the North China Block. In addition, the development of WNW-directed faults in the southern Liaodong Bay subbasin was conducive to the formation of buried Mesozoic and Paleozoic hills and hydrocarbon accumulations. In addition, we suggest that the compressional segment of the conjugated strike-slip transition zone that was formed by the interaction of the WNW- and NNE-directed strike-slip faults was conducive to hydrocarbon accumulations.

The tectonic transition from rifting to strike-slip in the Liaodong Bay Depression, offshore China

The Liaodong Bay Depression was shaped by the Bohai Bay rift basin (BBRB) and the Tan-Lu strike-slip fault system (TSFS) in the Cenozoic and has undergone a tectonic transition from rifting to strike-slip. Therefore, it is an ideal region to study the transition from rifting to strike-slip. Based on new 3D serial seismic data interpretation, we investigated the types and formation times of the main faults in the Liaodong Bay Depression and restored them within the palaeogeography of each evolution stage. Our results show that the Liaodong Bay Depression underwent a tectonic transition from rifting to strike-slip: (1) The mantle material upsurge caused by the Izanagi plate trapped in the mantle transition zone led to rifting of the Liaodong Bay Depression from the Palaeocene to the Eocene. (2) In the middle Eocene, the change in the subduction direction of the Pacific plate led to dextral strike-slip movement along the Tan-Lu fault zone. (3) The rifting and strike-slip in the Liaodong Bay depression are related, and the transition from rifting to strike-slip occurred from the middle Eocene to the early Oligocene. The strike-slip faults developed when rifting was weak in the Oligocene. The transition from rifting to strike-slip faulting formed oil-gas accumulation zones along the strike-slip fault zone and thus resulted in the good oil and gas exploration prospects of this area.

Automatic and Accurate Extraction of Sea Ice in the Turbid Waters of the Yellow River Estuary Based on Image Spectral and Spatial Information

Sea ice is an important part of the global cryosphere and an important variable in the global climate system. Sea ice also presents one of the major natural disasters in the world. The automatic and accurate extraction of sea ice extent is of great significance for the study of climate change and disaster prevention. The accuracy of sea ice extraction in the Yellow River Estuary is low due to the large dynamic changes in the suspended particulate matter (SPM). In this study, a set of sea ice automatic extraction method systems combining image spectral information and textural information is developed. First, a sea ice spectral information index that can adapt to sea areas with different turbidity levels is developed to mine the spectral information of different types of sea ice. In addition, the image’s textural feature parameters and edge point density map are extracted to mine the spatial information concerning the sea ice. Then, multi-scale segmentation is performed on the image. Finally, the OTSU algorithm is used to determine the threshold to achieve automatic sea ice extraction. The method was successfully applied to Gaofen-1 (GF1), Sentinel-2, and Landsat 8 images, where the extraction accuracy of sea ice was over 93%, which was more than 5% higher than that of SVM and K-Means. At the same time, the method was applied to the Liaodong Bay area, and the extraction accuracy reached 99%. These findings reveal that the method exhibits good reliability and robustness.

Spatio‐temporal distribution and genetic mechanism of Paleogene extension amounts in the Liaodong Bay, Bohai Bay Basin

Based on seismic interpretation of 18 regional 3D high‐resolution seismic sections across Liaodong Bay, extension amounts, extension rates and extension coefficients of different seismic sections from the south to the north are calculated by employing balanced section technique. Then, spatio‐temporal distribution of extension amounts is characterized and interpreted. Finally, the analysis of genetic mechanism is conducted and analysed. The results indicate that tectonic evolution in the Paleogene of Liaodong Bay is characterized by episodic extension. Furthermore, spatio‐temporal distribution of extension amounts is relatively uneven. In terms of space, extension amounts are mainly caused by extensional displacement of main depression‐controlled boundary faults and syn‐depositional faults in the depression. In addition, extensional amounts along main depression‐controlled boundary faults are characterized by larger displacement. In terms of time, the periods for horizontal extensional movement can be divided into three stages: The Palaeocene‐Early Eocene (Kongdian Formation‐third member of Shahejie Formation), Middle‐Late Eocene‐Early Oligocene (first and second member of Shahejie Formation) and Middle‐Late Oligocene (Dongying Formation). Among them, extension during the Palaeocene‐Early Eocene occurs both in the north and south of Liaodong Bay. However, extension intensity in the north is stronger than that in the south. Extension intensity in the middle and north during Middle‐Late Eocene‐Early Oligocene obviously increases. In contrast, it is dominated by strike‐slip movement during depositional period of Dongying Formation. Therefore, extension intensity is characterized by significant inheritance. Spatial–temporal distribution of extension amounts is predominantly controlled by tectonic evolution and associated tectonic deformation.

Trends and Health Risk of Trace Metals in Fishes in Liaodong Bay, China, From 2015 to 2020

Due to their toxicity, non-biodegradability, and biological amplification in the food chain, heavy metal accumulation in humans via the consumption of fishes has become a problem. In this study, we analyzed the concentrations of six trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in 12 marine fish species collected from Liaodong Bay, China, from 2015 to 2020, to understand the pollution status of the bay and evaluate the impact of fish consumption on human health. In addition, 5 fish species with the potential to serve as bioindicators of metal contamination were identified. In general, the average concentrations were Zn > Pb ≈ Cr > Ni ≈ Cu > Cd. There were significant differences in the concentrations in the muscle tissues of fish with different feeding strategies. The total target hazard quotient values of some fish were greater than 1 in 2015, suggesting that people were susceptible to high health risks. The year 2017 had the lowest values, which suggests that metal pollution in Liaodong Bay may have been decreasing at that time. Monitoring of metal concentrations in marine fish from Liaodong Bay warrants more study.

Behaviors and trophodynamics of o,p′-dichlorodiphenyltrichloroethane (o,p′-DDT) in the aquatic food web: Comparison with p,p′-DDT

The broad-spectrum insecticide p,p′-dichlorodiphenyltrichloroethane (p,p′-DDT) has been banned in most countries since the 1970s on account of its environmental persistence as well as the high biomagnification of its major metabolite 1,1-dichloro-2,2-bis(4-chorophenyl)ethylene (p,p′-DDE). However, the information on the bioaccumulation and behavior of p,p′-DDTs in aquatic organisms is lacking. In this study, all 6 DDT isomers were detected in biota from the food web of the Liaodong Bay, China, and the total concentrations of DDT isomers in Chinese anchovy (Thrissa kammalensis) and Japanese Spanish mackerel (Scomberomrus niphonius) were 223 ± 42 ng/g ww and 242 ± 70 ng/g ww, respectively. In biota, o,p′-DDD dominated among the o,p′-isomers (80.5 ± 17.3%), while p,p′-DDE dominated among the p,p′-isomers (61.8 ± 15.2%). Contrastingly, sediment from the Liaodong Bay contained similar proportions of o,p′-DDT and p,p′-DDTs, suggesting an isomer-specific metabolism of the compounds in biota. A well-controlled laboratory exposure experiment with Japanese medaka (Oryzias latipes) demonstrated that o,p′-DDT was more difficult to metabolize to o,p′-DDE compared with that of p,p′-DDT. Significantly positive regressions were found between trophic levels and lipid equivalent concentrations for both o,p′-DDT and o,p′-DDD, and the trophic magnification factors (TMFs) were estimated as 12.3 and 9.12 (p < 0.05), respectively. The TMFs of o,p′-DDT and o,p′-DDD in the aquatic food web were higher than p,p′-DDT (7.76), p,p′-DDD (4.17), and p,p′-DDE (3.39), which may be explained by the isomer-specific metabolism differences in biota.

Seasonal and Spatial Variation in Dissolved Heavy Metals in Liaodong Bay, China.

Spatial–seasonal variations in dissolved heavy metals in surface seawater were analyzed based on surveys at 87 sampling sites and water samples from six rivers across Liaodong Bay. The concentrations of copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) had ranges of 0.20–40.00 (5.45 ± 5.67), 0.51–33.64 (4.68 ± 3.93), 0.03–13.47 (2.22 ± 2.01), and 0.50–80.09 μg/L (14.22 ± 16.32), respectively, throughout the four seasons of 2020. The trace metal concentration showed a spatial gradient of high to low from river to estuary and from inshore to offshore areas. A combination of pollution levels and marine sensitivity was employed to assess the pollution degree of the heavy metals. As a whole, the single pollution factors of trace metals in Liaodong Bay were ranged in the order Pb > Zn > Cu > Cd. The total pollution degree was relatively high in autumn and summer due to increased riverine inputs after the rainy season, while relatively low in spring and winter. These findings provide baseline data for future targeting policies to protect marine environments in Liaodong Bay.

First record of the non-native jellyfish Chrysaora pacifica (Goette, 1886) (Cnidaria, Scyphozoa) in Liaodong Bay, Bohai Sea, China

First record of the non-native jellyfish Chrysaora pacifica (Goette, 1886) (Cnidaria, Scyphozoa) in Liaodong Bay, Bohai Sea, China

Sequence architecture, depositional evolution and responses to tectonic subsidence and lacustrine fluctuation in lacustrine rift basin: A case study from Cenozoic Liaodong Bay, Bohai Bay Basin

The sequence architecture and depositional evolution in Cenozoic Liaodong Bay, Bohai Bay Basin are formed mainly in response to rifting and lacustrine fluctuations which have been documented by integrated analysis of seismic reflections, well logs, lithology associations and core analysis. Four depositional-geomorphological systems are identified comprising fan delta systems, near-shore subaqueous fan systems, beach-bar systems and braided river delta systems. Three composite sequences (CS) are recognized including CS IV (S4), CS III (S3-3, S3-2, S3-1), and CS II (S2). The identification and description of sequence boundaries in different composite sequences vary from each other due to database. CS IV (S4) is difficult to identify across the whole area. CS III (S3-3, S3-2, S3-1) is bounded by regional unconformities along the slope or on the uplift and correlative conformities in the central depression. CS II (S2) is locally bounded by regional unconformities according to seismic resolution. The geomorphical processes and fault activities, during different stages of rifting, in addition to overlapping effects of lacustrine fluctuations, sediment supply and climate changes control composite sequences and depositional-geomorphological systems. Finally, fan delta systems and braided river delta systems are proposed to host petroleum reserves.